What is Docker?

Docker is a containerization platform that allows you to package applications and their dependencies into lightweight, portable containers that can run consistently across different environments.

Understanding Docker

Docker was released by Docker Inc. in 2013 and has revolutionized how applications are developed, shipped, and deployed. It solves the "it works on my machine" problem by ensuring applications run the same way everywhere.

Key Features of Docker

1. Containerization

Applications are packaged with all their dependencies, libraries, and configuration files into isolated containers.

2. Portability

Containers can run on any system that has Docker installed, regardless of the underlying operating system.

3. Consistency

The same container will behave identically across development, testing, and production environments.

4. Isolation

Each container runs in its own isolated environment, preventing conflicts between applications.

Basic Docker Example

# Dockerfile
FROM node:18-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3000
CMD ["npm", "start"]

# Build and run a container
docker build -t my-app .
docker run -p 3000:3000 my-app

Docker vs Traditional Virtualization

| Feature | Docker | Virtual Machines |

|---------|--------|------------------|

| Resource Usage | Lightweight | Heavy |

| Startup Time | Seconds | Minutes |

| Isolation Level | Process | OS |

| Image Size | Small | Large |

| Performance | Near-native | Overhead |

Why Use Docker?

Common Use Cases

Docker Ecosystem

Docker Commands

# Basic commands
docker images          # List images
docker ps             # List running containers
docker pull image     # Download image
docker run image      # Run container
docker stop container # Stop container
docker rm container   # Remove container

Docker has become essential in modern software development, enabling developers to build, ship, and run applications more efficiently and reliably.